 /*
  * $Header: /cvshome/build/org.osgi.service.useradmin/src/org/osgi/service/useradmin/Group.java,v 1.8 2006/06/16 16:31:41 hargrave Exp $
  *
  * Copyright (c) OSGi Alliance (2001, 2006). All Rights Reserved.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
  * http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
 package org.osgi.service.useradmin;

 /**
  * A named grouping of roles (<code>Role</code> objects).
  * <p>
  * Whether or not a given <code>Authorization</code> context implies a
  * <code>Group</code> object depends on the members of that <code>Group</code>
  * object.
  * <p>
  * A <code>Group</code> object can have two kinds of members: <i>basic </i> and
  * <i>required </i>. A <code>Group</code> object is implied by an
  * <code>Authorization</code> context if all of its required members are implied
  * and at least one of its basic members is implied.
  * <p>
  * A <code>Group</code> object must contain at least one basic member in order to
  * be implied. In other words, a <code>Group</code> object without any basic
  * member roles is never implied by any <code>Authorization</code> context.
  * <p>
  * A <code>User</code> object always implies itself.
  * <p>
  * No loop detection is performed when adding members to <code>Group</code>
  * objects, which means that it is possible to create circular implications.
  * Loop detection is instead done when roles are checked. The semantics is that
  * if a role depends on itself (i.e., there is an implication loop), the role is
  * not implied.
  * <p>
  * The rule that a <code>Group</code> object must have at least one basic member
  * to be implied is motivated by the following example:
  *
  * <pre>
  *
  * group foo
  * required members: marketing
  * basic members: alice, bob
  *
  * </pre>
  *
  * Privileged operations that require membership in "foo" can be performed only
  * by "alice" and "bob", who are in marketing.
  * <p>
  * If "alice" and "bob" ever transfer to a different department, anybody in
  * marketing will be able to assume the "foo" role, which certainly must be
  * prevented. Requiring that "foo" (or any <code>Group</code> object for that
  * matter) must have at least one basic member accomplishes that.
  * <p>
  * However, this would make it impossible for a <code>Group</code> object to be
  * implied by just its required members. An example where this implication might
  * be useful is the following declaration: "Any citizen who is an adult is
  * allowed to vote." An intuitive configuration of "voter" would be:
  *
  * <pre>
  *
  * group voter
  * required members: citizen, adult
  * basic members:
  *
  * </pre>
  *
  * However, according to the above rule, the "voter" role could never be assumed
  * by anybody, since it lacks any basic members. In order to address this issue
  * a predefined role named "user.anyone" can be specified, which is always
  * implied. The desired implication of the "voter" group can then be achieved by
  * specifying "user.anyone" as its basic member, as follows:
  *
  * <pre>
  *
  * group voter
  * required members: citizen, adult
  * basic members: user.anyone
  *
  * </pre>
  *
  * @version $Revision: 1.8 $
  */
 public interface Group extends User {
     /**
      * Adds the specified <code>Role</code> object as a basic member to this
      * <code>Group</code> object.
      *
      * @param role The role to add as a basic member.
      *
      * @return <code>true</code> if the given role could be added as a basic
      * member, and <code>false</code> if this <code>Group</code> object
      * already contains a <code>Role</code> object whose name matches that
      * of the specified role.
      *
      * @throws SecurityException If a security manager exists and the caller
      * does not have the <code>UserAdminPermission</code> with name
      * <code>admin</code>.
      */
     public boolean addMember(Role role);

     /**
      * Adds the specified <code>Role</code> object as a required member to this
      * <code>Group</code> object.
      *
      * @param role The <code>Role</code> object to add as a required member.
      *
      * @return <code>true</code> if the given <code>Role</code> object could be
      * added as a required member, and <code>false</code> if this
      * <code>Group</code> object already contains a <code>Role</code> object
      * whose name matches that of the specified role.
      *
      * @throws SecurityException If a security manager exists and the caller
      * does not have the <code>UserAdminPermission</code> with name
      * <code>admin</code>.
      */
     public boolean addRequiredMember(Role role);

     /**
      * Removes the specified <code>Role</code> object from this <code>Group</code>
      * object.
      *
      * @param role The <code>Role</code> object to remove from this <code>Group</code>
      * object.
      *
      * @return <code>true</code> if the <code>Role</code> object could be removed,
      * otherwise <code>false</code>.
      *
      * @throws SecurityException If a security manager exists and the caller
      * does not have the <code>UserAdminPermission</code> with name
      * <code>admin</code>.
      */
     public boolean removeMember(Role role);

     /**
      * Gets the basic members of this <code>Group</code> object.
      *
      * @return The basic members of this <code>Group</code> object, or
      * <code>null</code> if this <code>Group</code> object does not contain
      * any basic members.
      */
     public Role[] getMembers();

     /**
      * Gets the required members of this <code>Group</code> object.
      *
      * @return The required members of this <code>Group</code> object, or
      * <code>null</code> if this <code>Group</code> object does not contain
      * any required members.
      */
     public Role[] getRequiredMembers();
 }

